ABSTRACT: Euthyphro is a Socratic interlocutor claiming enormous religious expertise, while his portrayal in the eponymous dialogue raises questions the reliability of his beliefs. This paper closely examines how Euthyphro justifies his case against his father, identifying an argument that relies on the concept of miasma (pollution). In so far as miasma is considered in isolation, Euthyphro has a good argument. Unfortunately, there is more than miasma at stake when considering why one could prosecute one’s own parent. Introducing the other relevant concepts, honor and shame, we find his case reflects a dilemma at the source of ancient Greek religious thought. It would not be possible for Euthyphro or anyone else to know what to do in his case.